Method for processing peripheral portion of thin plate and apparatus therefor

ABSTRACT

A method for processing a peripheral portion of a thin plate, comprises the steps of; contacting the thin plate with a processing part of a tool, which has a round free end and projects to the thin plate in order to process the contacted peripheral portion of the thin plate, and moving at least one selected from the tool and the thin plate in a direction of the other, which is parallel to a main surface of the thin plate and in a direction of the other, which is normal to the main surface of the thin plate, in order to change one contacting point between the peripheral portion of the thin plate and the processing part of the tool to another contacting point and to process the changed contacting point of the peripheral portion of the thin plate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for processing a peripheralportion of a thin plate, such as a silicon wafer and an apparatustherefor.

2. Description of the Related Art

A shock (impact) load is applied to a peripheral portion of a siliconwafer when a lapping step or a double side polishing step is carried outin a process of manufacturing silicon wafers. A shock load is applied toa peripheral portion of a wafer in a process of manufacturingsemiconductor elements because of a thermal stress caused by a heatingand cooling treatment between room temperature and one thousand andseveral hundred degrees centigrade or because of a film formingtreatment, such as an oxidation. Further, a shock load is applied to aperipheral portion of a wafer locally and frequently because a wafer ispositioned, a wafer is transferred inside an apparatus, a wafer istransferred between one apparatus and another, a wafer is supported orthe like by using a peripheral portion of the wafer in the process ofmanufacturing silicon wafers and in the process of manufacturingsemiconductor elements.

When the shock load is applied to a peripheral portion of a waferlocally, the peripheral portion of the wafer is liable to be chippedoff. Because the Si wafer which is a material for semiconductor elementsis made of a silicon and is a single crystal, the wafer has a cleavagedepending on a crystal orientation thereof and is brittle. When thewafer is chipped off, small fragments thereof fly. Because the smallfragments adhere to the surface of the wafer, on which the semiconductorelements are formed, the characteristics of the semiconductor elementsand the yield thereof are deteriorated.

The peripheral portion of the wafer has been chamfered in order to avoidor relieve these problems according to an earlier development.

Next, the typical three types of the chamfering apparatus will beexplained below.

The first chamfering apparatus is a formed chamfering apparatus shown inFIG. 7. The chamfering apparatus 100 comprises a grinding wheel 101 (aso-called formed grinding wheel) having a groove of which shape is thesame as that of a chamfered portion. The wafer W is held on the holdingtable 102 by using a vacuum chuck. In this chamfering apparatus 100, thegrinding wheel 101 is pushed to the wafer W by applying a constant loadthereto in order to process the peripheral portion of the wafer W.According to the chamfering apparatus 100, the shape of the chamferedportion of the wafer W is determined by the shape of the groove of thegrinding wheel 101.

The second chamfering apparatus is a copy chamfering apparatus shown inFIG. 8. The chamfering apparatus 200 comprises a grinding wheel 201having a groove 201 a of which width is larger than the thickness of thewafer W. The wafer W is sandwiched by a pair of holding bodies 202 and203 disposed at upper and lower positions of the wafer W to besandwiched in order to hold the wafer W. In the chamfering apparatus200, a copy model 204 is disposed on the same axis as the upper holdingbody 202. The copy model 204 and the upper holding body 202 rotatetogether and move in a vertical direction. A copy roller 205 is disposedon the same axis as the grinding wheel 201. The copy roller 205 and thegrinding wheel 201 rotate independently of each other.

The process of chamfering the peripheral portion of the wafer is carriedout by using the chamfering apparatus 200 as follows. That is, after thewafer W was sandwiched, the copy roller 205 moves in a direction of thecopy model 204. The copy roller 205 and the copy model 204 roll in orderto contact with each other. While the copy roller 205 moves, thegrinding wheel 201 contacts the wafer W in order to start chamfering theperipheral portion of the wafer W. In the chamfering process, theperipheral portion of the wafer W is processed by rotating the wafer Wby one rotation. The wafer W is moved upwardly and is rotated by onerotation in order to chamfer the upper surface of the peripheral portionof the wafer W. The wafer W is moved downwardly and is rotated by onerotation in order to chamfer the lower surface of the peripheral portionof the wafer W.

In the chamfering apparatus 200, because the diameter of the grindingwheel 201, which is measured on the basis of the bottom of the groove201 a is the same as that of the copy roller 205, the diameter of thewafer W is the same as that of the copy model 204. The upper surface ofthe peripheral portion of the wafer W is processed by the upper wall ofthe groove 201 a. The lower surface of the peripheral portion of thewafer W is processed by the lower wall of the groove 201 a. As a result,the shape of the upper part of the chamfered portion corresponds to thatof the upper wall of the groove 201 a. Similarly, the shape of the lowerpart of the chamfered portion corresponds to that of the lower wall ofthe groove 201 a. Further, the width of the chamfered portion isdetermined by the positions in which the wafer W is disposed when thewafer W is moved upwardly and when the wafer W is moved downwardly.

The third chamfering apparatus is an NC (numerical control) chamferingapparatus which is not shown in the drawings. The chamfering apparatuscarries out the control of the relative positions of the wafer and thegrinding wheel not by using the copy roller and the copy model like thecopy chamfering apparatus, but by the NC control. The process ofchamfering the peripheral portion of the wafer is carried out similarlyto the copy chamfering apparatus.

The function of the chamfered portion of the wafer is not only that thewafer is prevented from being chipped off. In particular, in case of awafer for making an epitaxial wafer, the chamfered portion of the waferprevents an extraordinary growth of an Si single crystal at theperipheral portion of the wafer. Further, the chamfered portion of thewafer drains liquid during a spin coat in a resisting step. It isdecided by the cross-sectional shape of the chamfered portion of thewafer (hereinafter, referred to as “chamfer shape”) and by the sizethereof which function of the chamfered portion is superior to another.It is necessary to select the chamfer shape and the size of thechamfered portion suitably by considering which function is important.For example, the chamfer shape is a semicircular shape, a trapezoidalshape, a shape in which an end of a trapezoid is round or the like.There are various sizes of the chamfered portion.

However, in the three types of chamfering apparatus, because the chamfershape is determined by the shape of the groove of the grinding wheel, itis necessary that one grinding wheel should be changed for anotherhaving a different groove from one grinding wheel when the shape of thechamfered portion is changed. Several types of grinding wheels must beprepared in order to change one grinding wheel for another. It istroublesome to change one grinding wheel for another. Further, there isa problem that a chamfering apparatus cannot be operated while onegrinding wheel is changed for another.

SUMMARY OF THE INVENTION

The present invention was developed in view of these problems.

An object of the present invention is to provide a processing method forprocessing several types of chamfered portions or the like withoutchanging one tool for another and a processing apparatus therefor.

That is, in accordance with one aspect of the present invention, themethod for processing a peripheral portion of a thin plate, comprisesthe steps of; contacting the thin plate with a processing part of atool, which has a round free end and projects to the thin plate in orderto process the contacted peripheral portion of the thin plate, andmoving at least one selected from the tool and the thin plate in adirection of the other, which is parallel to a main surface of the thinplate and in a direction of the other, which is normal to the mainsurface of the thin plate, in order to change one contacting pointbetween the peripheral portion of the thin plate and the processing partof the tool to another contacting point and to process the changedcontacting point of the peripheral portion of the thin plate.

In the specification, the word “process” means the process of thechamfered portion, that is, making the chamfered portion and polishingthe chamfered portion, if other meanings of the word “process” are notgiven especially.

According to the method for processing the peripheral portion of thethin plate, because the step of contacting the thin plate with aprocessing part of a tool, which has a round free end and projects tothe thin plate in order to process the contacted peripheral portion ofthe thin plate, and the step of moving at least one selected from thetool and the thin plate in a direction of the other, which is parallelto a main surface of the thin plate and in a direction of the other,which is normal to the main surface of the thin plate, in order tochange one contacting point between the peripheral portion of the thinplate and the processing part of the tool to another contacting pointand to process the changed contacting point of the peripheral portion ofthe thin plate, are carried out, the peripheral portion of the thinplate can be processed by using each point of the processing part of thetool. As a result, the chamfered portions having various shapes can beproperly made by one tool. When the tool for making the chamferedportion is changed for one for polishing the chamfered portion, thechamfered portions having various shapes can be polished. Because a loadis dispersed into a whole processing part without applying it to aspecific position of the tool, a life of the tool can be longer.

The moving step may be carried out by moving at least one selected fromthe tool and the thin plate further in a direction normal to thedirection of the other, which is parallel to the main surface of thethin plate and to the direction of the other, which is normal to themain surface of the thin plate.

According to the method of processing the peripheral portion of the thinplate, even though the peripheral portion of the thin plate is composedof a linear form, the peripheral portion of the thin plate can beprocessed.

The processing part of the tool may comprise a flat portion of whichupper and lower surfaces are parallel to each other.

A gentle slope part which is a boundary part between the chamferedportion and the main surface of the thin plate can be properlyprocessed.

A thickness of the processing part may be two or more times larger thanthat of the thin plate. A radius of curvature of the round free end ofthe processing part may be larger than a half of a thickness of the flatportion of the processing part. The tool may have a cylindrical shapeand the processing part attached to a circumferential portion of thetool has a ring shape.

In accordance with another aspect of the present invention, the methodfor processing a peripheral portion of a thin plate, comprises the stepsof; contacting the thin plate with a processing part of a tool, whichhas a groove having a round bottom so as to surround the peripheralportion of the thin plate with the processing part from three differentdirections from one another, in order to process the contactedperipheral portion of the thin plate, and moving at least one selectedfrom the tool and the thin plate in a direction of the other, which isparallel to a main surface of the thin plate and in a direction of theother, which is normal to the main surface of the thin plate, in orderto change one contacting point between the peripheral portion of thethin plate and the processing part of the tool to another contactingpoint and to process the changed contacting point of the peripheralportion of the thin plate.

The opening width of the groove is not less than 1000 μm preferably whenthe thicknesses of the thin plates are from 500 μm to 900 μm. It isnecessary that the opening width of the groove is not less than 1000 μmin order to process these thin plates by using one tool.

Because the step of contacting the thin plate with a processing part ofa tool, which has a groove having a round bottom so as to surround theperipheral portion of the thin plate with the processing part from threedifferent directions from one another, in order to process the contactedperipheral portion of the thin plate, and the step of moving at leastone selected from the tool and the thin plate in a direction of theother, which is parallel to a main surface of the thin plate and in adirection of the other, which is normal to the main surface of the thinplate, in order to change one contacting point between the peripheralportion of the thin plate and the processing part of the tool to anothercontacting point and to process the changed contacting point of theperipheral portion of the thin plate, are carried out, the peripheralportion of the thin plate can be processed by using each point of theprocessing part of the tool. As a result, the chamfered portions of thethin plate having a thickness smaller than the opening width can beproperly made by one tool.

The moving step may be carried out by moving at least one selected fromthe tool and the thin plate further in a direction normal to thedirection of the other, which is parallel to the main surface of thethin plate and to the direction of the other, which is normal to themain surface of the thin plate.

According to the method of processing the peripheral portion of the thinplate, even though the peripheral portion of the thin plate is composedof a linear form, the peripheral portion of the thin plate can beprocessed.

A depth of the groove is larger than a width of a chamfered portion ofthe thin plate.

A gentle slope part which is a boundary part between the chamferedportion and the main surface of the thin plate can be properlyprocessed.

In accordance with another aspect of the present invention, theapparatus for processing a peripheral portion of a thin plate,comprises; a tool having a processing part which has a round free endand projects to the thin plate, a contacting device for contacting thethin plate with the processing part of the tool in order to process thecontacted peripheral portion of the thin plate, and a moving device formoving at least one selected from the tool and the thin plate in adirection of the other, which is parallel to a main surface of the thinplate and in a direction of the other, which is normal to the mainsurface of the thin plate, in order to change one contacting pointbetween the peripheral portion of the thin plate and the processing partof the tool to another contacting point and to process the changedcontacting point of the peripheral portion of the thin plate.

According to the apparatus for processing the peripheral portion of thethin plate, the peripheral portion of the thin plate can be processed byusing each point of the processing part of the tool. As a result, thechamfered portions having various shapes can be properly made by onetool. When the tool for making the chamfered portion is changed for onefor polishing the chamfered portion, the chamfered portions havingvarious shapes can be polished. Because a load is dispersed into a wholeprocessing part without applying it to a specific position of the tool,a life of the tool can be longer.

The moving device may move at least one selected from the tool and thethin plate further in a direction normal to the direction of the other,which is parallel to the main surface of the thin plate and to thedirection of the other, which is normal to the main surface of the thinplate.

According to the apparatus for processing the peripheral portion of thethin plate, even though the peripheral portion of the thin plate iscomposed of a linear form, the peripheral portion of the thin plate canbe processed.

The processing part of the tool may comprise a flat portion of whichupper and lower surfaces are parallel to each other.

A gentle slope part which is a boundary part between the chamferedportion and the main surface of the thin plate can be properlyprocessed.

A thickness of the processing part may be two or more times larger thanthat of the thin plate. A radius of curvature of the round free end ofthe processing part may be larger than a half of a thickness of the flatportion of the processing part. The tool may have a cylindrical shapeand the processing part attached to a circumferential portion of thetool has a ring shape.

In accordance with another aspect of the present invention, theapparatus for processing a peripheral portion of a thin plate,comprises; a tool having a processing part which has a groove having around bottom, a contacting device for contacting the thin plate with theprocessing part of the tool so as to surround the peripheral portion ofthe thin plate with the processing part from three different directionsfrom one another, in order to process the contacted peripheral portionof the thin plate, and a moving device for moving at least one selectedfrom the tool and the thin plate in a direction of the other, which isparallel to a main surface of the thin plate and in a direction of theother, which is normal to the main surface of the thin plate, in orderto change one contacting point between the peripheral portion of thethin plate and the processing part of the tool to another contactingpoint and to process the changed contacting point of the peripheralportion of the thin plate.

According to the apparatus for processing the peripheral portion of thethin plate, the peripheral portion of the thin plate can be processed byusing each point of the processing part of the tool. As a result, thechamfered portions of the thin plate having a thickness smaller than theopening width can be properly made by one tool.

The moving device may move at least one selected from the tool and thethin plate further in a direction normal to the direction of the other,which is parallel to the main surface of the thin plate and to thedirection of the other, which is normal to the main surface of the thinplate.

According to the apparatus for processing the peripheral portion of thethin plate, even though the peripheral portion of the thin plate iscomposed of a linear form, the peripheral portion of the thin plate canbe processed.

A depth of the groove is larger than a width of a chamfered portion ofthe thin plate.

A gentle slope part which is a boundary part between the chamferedportion and the main surface of the thin plate can be properlyprocessed.

According to the present invention, because the step of contacting thethin plate with a processing part of a tool, which has a round free endand projects to the thin plate in order to process the contactedperipheral portion of the thin plate, and the step of moving at leastone selected from the tool and the thin plate in a direction of theother, which is parallel to a main surface of the thin plate and in adirection of the other, which is normal to the main surface of the thinplate, in order to change one contacting point between the peripheralportion of the thin plate and the processing part of the tool to anothercontacting point and to process the changed contacting point of theperipheral portion of the thin plate, are carried out, the peripheralportion of the thin plate can be processed by using each point of theprocessing part of the tool. As a result, the chamfered portions havingvarious shapes can be properly made by one tool. When the tool formaking the chamfered portion is changed for one for polishing thechamfered portion, the chamfered portions having various shapes can bepolished.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not intendedas a definition of the limits of the present invention, and wherein;

FIG. 1 is a view schematically showing an embodiment of the chamferingapparatus (a processing apparatus) according to the present invention;

FIG. 2 is a block diagram showing the chamfering apparatus shown in FIG.1;

FIG. 3 is a view showing a state that the wafer set in the chamferingapparatus contacts the grinding wheel according to the first example;

FIG. 4 is a view showing a state that the wafer contacts the grindingwheel according to the second example;

FIG. 5 is a view showing a state that the wafer contacts the grindingwheel according to the third example;

FIG. 6 is a view showing a state that the wafer contacts the grindingwheel according to the fourth example;

FIG. 7 is a view schematically showing a chamfering apparatus accordingto an earlier development; and

FIG. 8 is a view schematically showing another chamfering apparatusaccording to an earlier development.

PREFERRED EMBODIMENT OF THE INVENTION

FIG. 1 shows a chamfering apparatus (a processing apparatus) accordingto the embodiment of the present invention. FIG. 2 shows a block diagramthereof. The chamfering apparatus 1 comprises a holding table 2 forholding a wafer W by a vacuum chuck, a reciprocating table 3 forsupporting the holding table 2 so as to move it in a direction normal tothe surface of the sheet in the case of the apparatus shown in FIG. 1(Y-direction), a holding table moving member 4 for moving the holdingtable 2 in the Y-direction on the reciprocating table 3, a reciprocatingtable moving member 5 for moving the reciprocating table 3 reciprocallyin a direction of the arrow X (X-direction), a wafer rotating member 7for rotating the holding table 2 and the wafer W on the first axis 6, alifting table 9 for supporting a grinding wheel 8, a lifting tablemoving member 10 for moving the lifting table 9 in a direction of thearrow Z (Z-direction) and a grinding wheel rotating member 12 forrotating the grinding wheel 8 on the second axis 11. As shown in FIG. 2,the chamfering apparatus 1 comprises a detecting member 13 for detectinga position of the holding table 2 and the wafer W and a state that theholding table 2 and the wafer W rotate, and a numerical control device14 for controlling the holding table moving member 4, the reciprocatingtable moving member 5, the wafer rotating member 7 and the lifting tablemoving member 10 on the basis of a signal outputted from the detectingmember 13. A contacting device for contacting the wafer W with thegrinding wheel 8 precisely and changing a contacting point between thewafer W and the grinding wheel 8, is composed of the holding tablemoving member 4, the reciprocating table moving member 5 and the liftingtable moving member 10. A sliding member for sliding the wafer W and thegrinding wheel 8 relatively to each other, is composed of the waferrotating member 7 and the grinding wheel rotating member 12.

Although the present invention is not limited to the thickness of thegrinding wheel 8, the grinding wheel 8 is thicker than the wafer W asshown in FIG. 3. In consideration of practical use, such as the wear ofthe grinding wheel 8, a processing part 8 a of the grinding wheel 8 isat least two or more times thicker than the wafer W, preferably. Theshape of the grinding wheel 8 is a disk of which a peripheral portionprojects in an arched form. In the concrete, the peripheral portion ofthe grinding wheel 8 projects in a semicircular form in consideration ofpractical use that the grinding wheel 8 is easily manufactured and theprogram for operating the reciprocating table 3 and the lifting table 9is easily composed. The projection part of the grinding wheel 8 is theprocessing part 8 a having a round free end.

Next, the operations of the chamfering apparatus 1 constructed asdescribed above will be explained below.

The wafer W is held on the holding table 2. While the wafer W isrotated, the reciprocating table 3 is moved in order to contact theperipheral portion of the wafer W with the grinding wheel 8. At the sametime, the grinding wheel 8 is rotated. When the peripheral portion ofthe wafer W starts to be chamfered, the reciprocating table 3 and thelifting table 9 are moved in order to move the grinding wheel 8 withrespect to the wafer W in the X-direction and the Z-directionrelatively. Thereby, the circumferential portion of the wafer W ischamfered.

When a linear part of the peripheral portion of the wafer W (anorientation flat portion) is chamfered, only the grinding wheel 8 isrotated. The grinding wheel 8 is moved with respect to the wafer W inthe X-direction, the Y-direction and the Z-direction relatively.

According to the chamfering apparatus 1 constructed as described above,the grinding wheel 8 having the processing part 8 a projecting in anarched form is used. Because the peripheral portion of the wafer W isprocessed by moving the grinding wheel 8 with respect to the wafer W inthe X-direction, the Y-direction and the Z-direction relatively, theperipheral portion of the wafer W can be processed by using each pointof the processing part 8 a of the grinding wheel 8. As a result, thechamfered portions having various shapes can be properly made by onegrinding wheel 8.

In order to confirm this effect, the chamfer shape was made by grindingthe peripheral portion of the Si wafer obtained by slicing an ingot,which had a diameter of 201.0 mm and a thickness of 750 μm according tothe present invention. As an example of a chamfered portion, the shapeof the chamfered portion was composed of a circular arc form having aradius of curvature of 400 μm, a line having a slope of 22° with respectto the main surface of the wafer, and a circular arc having a radius ofcurvature of 300 μM. Further, they were connected smoothly. As a tool, ametal bonded diamond grinding wheel having an outer diameter of 80 mm,which had a projection on the peripheral portion thereof, of which crosssection had a semicircular form having a radius of curvature of 3 mm, isused. In order to obtain the predetermined chamfer shape, the relativepositions of the wafer and the grinding wheel were calculatedgeometrically on the basis of the diameter of the wafer as a target, thechamfer shape and the size of the grinding wheel. The amounts ofmovements of the reciprocating table, the lifting table and the holdingtable were determined in order to compose a program. The program wasinputted into the numerical control device. In the grinding conditions,the rotating speed of the grinding wheel was set to 4000 rpm, that ofthe wafer was set to 30 rpm and the sliding speed of the grinding wheelwas set to 1 mm/min. Water was used as a grinding fluid.

The peripheral portion of the wafer was processed under theseconditions. After the process was finished, the chamfer shape wasmeasured by the enlarged projection method. It was confirmed that theperipheral portion of the wafer was processed in the desired shape.

FIG. 4 shows the second example of a grinding wheel. The shape of thegrinding wheel 80 is a disk of which peripheral portion projects. Theprojection part of the grinding wheel 80, that is, the processing part80 a has a flat portion of which upper and lower surfaces are parallelto each other, and a round free end having a radius of curvature whichis larger than a half of the thickness of the flat portion. FIG. 5 showsthe third example of a grinding wheel. The shape of the grinding wheel81 is a disk of which peripheral portion has a groove therearound. Thegroove has a bottom recessed in an arched form and a curved shoulderportion. The groove of the grinding wheel 81 is a processing part 81 a.The peripheral portion of the wafer W is chamfered in a state ofsurrounding the peripheral portion of the wafer W with the processingpart 81 a from three different directions from one another by using thegrinding wheel 81. The depth of the groove is larger than the width ofthe chamfered portion of the wafer W.

FIG. 6 shows the fourth example of a grinding wheel. The body part ofthe grinding wheel 82 has a cylindrical shape. The grinding wheel 82 hasa projection serving as a processing part 82 a on the circumferentialportion thereof. As shown in FIG. 6, the free end of the projection hasan arched form. The projection has a ring shape. In this case, as shownin FIG. 6, the length of the processing part 82 a is preferably largerthan the width of the chamfered portion of the wafer W because thegentle slope part which is a boundary part between the chamfered portionand the main surface can be properly processed.

Although the present invention has been explained according to theembodiment, it should also be understood that the present invention isnot limited to the embodiment and that various changes and modificationsmay be made to the invention without departing from the gist thereof.

For example, although it is explained that the peripheral portion of thewafer W is processed by using the grinding wheel, the present inventioncan be applied to the mirror-polishing of the chamfered portion, whichis carried out by using a buff made of a foamed urethane or the likeinstead of the grinding wheel and by using a colloidal silica as anabrasive slurry. In this case, the wafer can be contacted not only witha specific position of a polishing pad but also with a large areathereof. Because irregularities transferred from the polishing pad tothe wafer is averaged, a mirror-polished chamfered portion can be moresmooth.

The notch portion is chamfered by using a grinding wheel having a smalldiameter in order to make a chamfer shape like the above embodiment.

Although it is explained that the Si wafer is chamfered by the tool, thepresent invention can be applied to any thin plate.

It is thought that when a simple cylindrical grinding wheel is used, theobject of the present invention can be achieved by inclining therotation axis of the grinding wheel. However, according to the presentinvention, a thin plate can be properly processed without controllingthe rotation angle of the tool.

The entire disclosure of Japanese Patent Application No. Tokugan-Hei10-149934 filed on May 29, 1998 including specification, claims drawingsand summary are incorporated herein by reference in its entirety.

What is claimed is:
 1. A method for processing a peripheral portion of athin plate, comprising: contacting the peripheral portion of the thinplate with a processing part of a tool, which has a round free end andprojects to the thin plate, in order to process the contacted peripheralportion of the thin plate; and moving at least one selected from thetool and the thin plate in a direction of the other, which is parallelto a main surface of the thin plate while at least one selected from thetool and the thin plate is moved in a direction of the other, which isnormal to the main surface of the thin plate, in order to change onecontacting point between the peripheral portion of the thin plate andthe processing part of the tool to another contacting point and toprocess the changed contacting point of the peripheral portion of thethin plate; wherein a rotational axis of the tool is perpendicular tothe main surface of the thin plate.
 2. A method for processing aperipheral portion of a thin plate as claimed in claim 1, wherein themoving is carried out by moving at least one selected from the tool andthe thin plate further in a direction normal to the direction of theother, which is parallel to the main surface of the thin plate and tothe direction of the other, which is normal to the main surface of thethin plate.
 3. A method for processing a peripheral portion of a thinplate as claimed in claim 1, wherein the processing part of the toolcomprises a flat portion of which upper and lower surfaces are parallelto each other.
 4. A method for processing a peripheral portion of a thinplate as claimed in claim 1, wherein a thickness of the processing partis two or more times larger than that of the thin plate.
 5. A method forprocessing a peripheral portion of a thin plate as claimed in claim 3,wherein a radius of curvature of the round free end of the processingpart is larger than a half of a thickness of the flat portion of theprocessing part.
 6. A method for processing a peripheral portion of athin plate as claimed in claim 1, wherein the tool has a cylindricalshape and the processing part attached to a circumferential portion ofthe tool has a ring shape.
 7. A method for processing a peripheralportion of a thin plate, comprising: contacting the peripheral portionof the thin plate with a processing part of a tool, which has a groovehaving a round bottom so as to surround the peripheral portion of thethin plate with the processing part from three different directions fromone another, in order to process the contacted peripheral portion of thethin plate; moving at least one selected from the tool and the thinplate in a direction of the other, which is parallel to a main surfaceof the thin plate while at least one selected from the tool and the thinplate is moved in a direction of the other, which is normal to the mainsurface of the thin plate, in order to change one contacting pointbetween the peripheral portion of the thin plate and the processing partof the tool to another contacting point and to process the changedcontacting point of the peripheral portion of the thin plate.
 8. Amethod for processing a peripheral portion of a thin plate as claimed inclaim 7, wherein the moving step is carried out by moving at least oneselected from the tool and the thin plate further in a direction normalto the direction of the other, which is parallel to the main surface ofthe thin plate and to the direction of the other, which is normal to themain surface of the thin plate.
 9. A method for processing a peripheralportion of a thin plate as claimed in claim 7, wherein a depth of thegroove is larger than a width of a chamfered portion of the thin plate.10. An apparatus for processing a peripheral portion of a thin plate,comprising: a tool having a processing part which has a round free endand projects to the thin plate; a contacting device for contacting theperipheral portion of the thin plate with the processing part of thetool in order to process the contacted peripheral portion of the thinplate; and a moving device for moving at least one selected from thetool and the thin plate in a direction of the other, which is parallelto a main surface of the thin plate and in a direction of the other,which is normal to the main surface of the thin plate, in order tochange one contacting point between the peripheral portion of the thinplate and the processing part of the tool to another contacting pointand to process the changed contacting point of the peripheral portion ofthe thin plate; wherein a rotational axis of the tool is perpendicularto the main surface of the thin plate.
 11. An apparatus for processing aperipheral portion of a thin plate as claimed in claim 10, wherein themoving device moves at least one selected from the tool and the thinplate further in a direction normal to the direction of the other, whichis parallel to the main surface of the thin plate and to the directionof the other, which is normal to the main surface of the thin plate. 12.An apparatus for processing a peripheral portion of a thin plate asclaimed in claim 10, wherein the processing part of the tool comprises aflat portion of which upper and lower surfaces are parallel to eachother.
 13. An apparatus for processing a peripheral portion of a thinplate as claimed in claim 10, wherein a thickness of the processing partis two or more times larger than that of the thin plate.
 14. Anapparatus for processing a peripheral portion of a thin plate as claimedin claim 12, wherein a radius of curvature of the round free end of theprocessing part is larger than a half of a thickness of the flat portionof the processing part.
 15. An apparatus for processing a peripheralportion of a thin plate as claimed in claim 10, wherein the tool has acylindrical shape and the processing part attached to a circumferentialportion of the tool has a ring shape.
 16. An apparatus for processing aperipheral portion of a thin plate, comprising: a tool having aprocessing part which has a groove having a round bottom: a contactingdevice for contacting the thin plate with a processing part of a tool soas to surround the peripheral portion of the thin plate with theprocessing part from three different directions from one another, inorder to process the contacted peripheral portion of the thin plate; anda moving device for moving at least one selected from the tool and thethin plate in a direction of the other, which is parallel to a mainsurface of the thin plate while at least one selected from the tool andthe thin plate is moved in a direction of the other, which is normal tothe main surface of the thin plate, in order to change one contactingpoint between the peripheral portion of the thin plate and theprocessing part of the tool to another contacting point and to processthe changed contacting point of the peripheral portion of the thinplate.
 17. An apparatus for processing a peripheral portion of a thinplate as claimed in claim 16, wherein the moving device moves at leastone selected from the tool and the thin plate further in a directionnormal to the direction of the other, which is parallel to the mainsurface of the thin plate and to the direction of the other, which isnormal to the main surface of the thin plate.
 18. An apparatus forprocessing a peripheral portion of a thin plate as claimed in claim 16,wherein a depth of the groove is larger than a width of a chamferedportion of the thin plate.
 19. A method for processing a peripheralportion of a thin plate, comprising: contacting the peripheral portionof the thin plate with a processing part of a tool in order to processthe contacted peripheral portion of the thin plate, the processing partof the tool comprising a flat portion having upper and lower surfacesparallel to each other, and the processing part comprising a round freeend and projecting to the thin plate; and moving at least one selectedfrom the tool and the thin plate in a direction of the other, which isparallel to a main surface of the thin plate and in a direction of theother, which is normal to the main surface of the thin plate, in orderto change one contacting point between the peripheral portion of thethin plate and the processing part of the tool to another contactingpoint and to process the changed contacting point of the peripheralportion of the thin plate.
 20. A method for processing a peripheralportion of a thin plate, comprising: contacting the peripheral portionof the thin plate with a processing part of a tool in order to processthe contacted peripheral portion of the thin plate, the processing partof the tool comprising a flat portion having upper and lower surfacesparallel to each other, and the processing part comprising a round freeend and projecting to the thin plate, a radius of curvature of the roundfree end is larger than a half of a thickness of the flat portion of theprocessing part; and moving at least one selected from the tool and thethin plate in a direction of the other, which is parallel to a mainsurface of the thin plate and in a direction of the other, which isnormal to the main surface of the thin plate, in order to change onecontacting point between the peripheral portion of the thin plate andthe processing part of the tool to another contacting point and toprocess the changed contacting point of the peripheral portion of thethin plate.
 21. A method for processing a peripheral portion of a thinplate, comprising: contacting the peripheral portion of the thin platewith a processing part of a tool in order to process the contactedperipheral portion of the thin plate, the tool having a cylindricalshape and the processing part is attached to a circumferential portionof the tool and has a ring shape, the processing part having a roundfree end and projecting to the thin plate; and moving at least oneselected from the tool and the thin plate in a direction of the other,which is parallel to a main surface of the thin plate and in a directionof the other, which is normal to the main surface of the thin plate, inorder to change one contacting point between the peripheral portion ofthe thin plate and the processing part of the tool to another contactingpoint and to process the changed contacting point of the peripheralportion of the thin plate.
 22. An apparatus for processing a peripheralportion of a thin plate, comprising: a tool including a processing parthaving a round free end and projecting to the thin plate, the processingpart comprising a flat portion having upper and lower surfaces parallelto each other; a contacting device for contacting the peripheral portionof the thin plate with the processing part of the tool in order toprocess the contacted peripheral portion of the thin plate; and a movingdevice for moving at least one selected from the tool and the thin platein a direction of the other, which is parallel to a main surface of thethin plate and in a direction of the other, which is normal to the mainsurface of the thin plate, in order to change one contacting pointbetween the peripheral portion of the thin plate and the processing partof the tool to another contacting point and to process the changedcontacting point of the peripheral portion of the thin plate.
 23. Anapparatus for processing a peripheral portion of a thin plate,comprising: a tool including a processing part having a round free endand projecting to the thin plate, the processing part having a thicknesstwo or more times larger than that of the thin plate; a contactingdevice for contacting the peripheral portion of the thin plate with theprocessing part of the tool in order to process the contacted peripheralportion of the thin plate; and a moving device for moving at least oneselected from the tool and the thin plate in a direction of the other,which is parallel to a main surface of the thin plate and in a directionof the other, which is normal to the main surface of the thin plate, inorder to change one contacting point between the peripheral portion ofthe thin plate and the processing part of the tool to another contactingpoint and to process the changed contacting point of the peripheralportion of the thin plate.
 24. An apparatus for processing a peripheralportion of a thin plate, comprising: a tool including a processing parthaving a round free end and projecting to the thin plate, the processingpart comprising a flat portion having upper and lower surfaces parallelto each other, and a radius of curvature of the round free end is largerthan a half of a thickness of the flat portion of the processing part; acontacting device for contacting the peripheral portion of the thinplate with the processing part of the tool in order to process thecontacted peripheral portion of the thin plate; and a moving device formoving at least one selected from the tool and the thin plate in adirection of the other, which is parallel to a main surface of the thinplate and in a direction of the other, which is normal to the mainsurface of the thin plate, in order to change one contacting pointbetween the peripheral portion of the thin plate and the processing partof the tool to another contacting point and to process the changedcontacting point of the peripheral portion of the thin plate.
 25. Anapparatus for processing a peripheral portion of a thin plate,comprising: a tool including a processing part having a round free endand projecting to the thin plate, the tool having a cylindrical shapeand the processing part is attached to a circumferential portion of thetool and has a ring shape; a contacting device for contacting theperipheral portion of the thin plate with the processing part of thetool in order to process the contacted peripheral portion of the thinplate; and a moving device for moving at least one selected from thetool and the thin plate in a direction of the other, which is parallelto a main surface of the thin plate and in a direction of the other,which is normal to the main surface of the thin plate, in order tochange one contacting point between the peripheral portion of the thinplate and the processing part of the tool to another contacting pointand to process the changed contacting point of the peripheral portion ofthe thin plate.
 26. A method for processing a peripheral portion of athin plate, comprising: contacting the peripheral portion of the thinplate with a processing part of a tool in order to process the contactedperipheral portion of the thin plate, the processing part comprising around free end and projecting to the thin plate, and the processing parthaving a thickness at least two times larger than that of the thinplate; and moving at least one selected from the tool and the thin platein a direction of the other, which is parallel to a main surface of thethin plate and in a direction of the other, which is normal to the mainsurface of the thin plate, in order to change one contacting pointbetween the peripheral portion of the thin plate and the processing partof the tool to another contacting point and to process the changedcontacting point of the peripheral portion of the thin plate; wherein arotational axis of the tool is perpendicular to the main surface of thethin plate.